Who is in the top tier of the Republican 2016 presidential race? The lineup has been changing over the last few months, and it appears to have changed again.

At the beginning of this year, the only constant in the race was that Jeb Bush was in a leading position in the RealClearPolitics average of national polls. Rand Paul scored well, Mike Huckabee scored well, Ben Carson scored well — but there was no clearly discernible first tier of candidates.